WO2017109539A1 - Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet - Google Patents
Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet Download PDFInfo
- Publication number
- WO2017109539A1 WO2017109539A1 PCT/IB2015/059838 IB2015059838W WO2017109539A1 WO 2017109539 A1 WO2017109539 A1 WO 2017109539A1 IB 2015059838 W IB2015059838 W IB 2015059838W WO 2017109539 A1 WO2017109539 A1 WO 2017109539A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- temperature
- sheet
- steel sheet
- comprised
- partitioning
- Prior art date
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 53
- 239000010959 steel Substances 0.000 title claims abstract description 53
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 10
- 238000000638 solvent extraction Methods 0.000 claims abstract description 53
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 46
- 238000010791 quenching Methods 0.000 claims abstract description 42
- 230000000171 quenching effect Effects 0.000 claims abstract description 42
- 230000000717 retained effect Effects 0.000 claims abstract description 32
- 238000000137 annealing Methods 0.000 claims abstract description 30
- 238000001816 cooling Methods 0.000 claims abstract description 22
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 21
- 238000000034 method Methods 0.000 claims abstract description 19
- 238000010438 heat treatment Methods 0.000 claims abstract description 18
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 14
- 239000000203 mixture Substances 0.000 claims abstract description 13
- 239000010960 cold rolled steel Substances 0.000 claims abstract description 11
- 229910001563 bainite Inorganic materials 0.000 claims abstract description 10
- 239000000126 substance Substances 0.000 claims abstract description 10
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 238000005097 cold rolling Methods 0.000 claims description 8
- 238000010583 slow cooling Methods 0.000 claims description 5
- 238000005098 hot rolling Methods 0.000 claims description 4
- 239000011248 coating agent Substances 0.000 claims description 3
- 238000000576 coating method Methods 0.000 claims description 3
- 238000009713 electroplating Methods 0.000 claims description 3
- 238000001771 vacuum deposition Methods 0.000 claims description 3
- 229910052758 niobium Inorganic materials 0.000 abstract description 2
- 229910052719 titanium Inorganic materials 0.000 abstract description 2
- 229910052710 silicon Inorganic materials 0.000 description 10
- 229910052799 carbon Inorganic materials 0.000 description 9
- 239000011572 manganese Substances 0.000 description 9
- 230000015572 biosynthetic process Effects 0.000 description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 7
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 6
- 239000010703 silicon Substances 0.000 description 6
- 230000009466 transformation Effects 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 229910052748 manganese Inorganic materials 0.000 description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- 239000000470 constituent Substances 0.000 description 4
- 238000003303 reheating Methods 0.000 description 4
- 150000001247 metal acetylides Chemical class 0.000 description 3
- 238000002791 soaking Methods 0.000 description 3
- 230000001627 detrimental effect Effects 0.000 description 2
- 238000007571 dilatometry Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical class [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 2
- 229910052814 silicon oxide Inorganic materials 0.000 description 2
- 238000005496 tempering Methods 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 229910001297 Zn alloy Inorganic materials 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
- B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
- B32B15/013—Layered products comprising a layer of metal all layers being exclusively metallic one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or aluminium
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/06—Zinc or cadmium or alloys based thereon
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Definitions
- the present invention relates to a method for producing a high strength steel sheet having improved strength, ductility and formability and to the sheets obtained with the method.
- the partitioning time Pt is between 50 and 200 s.
- the invention also relates to a steel sheet, wherein the chemical composition of the steel contains in weight %:
- the silicon content is higher than or equal to 1 .9%, still preferably higher than or equal to 2.0%.
- An increased amount of silicon improves the hole expansion ratio.
- the silicon content is lower than or equal to 2.2%. A silicon content above 2.3% would lead to formation of silicon oxides at the surface.
- the hot rolled sheet can be pickled and cold rolled to obtain a cold rolled sheet having a thickness between 0.5 mm and 2.5 mm.
- the annealing temperature T A is of at most Ac3 + 50°C, in order to limit the coarsening of the austenitic grains.
- the annealing temperature T A is of at most Ac3.
- Ac3 designates the temperature of start and the end of the transformation into austenite during the heating step.
- the sheet is maintained at the annealing temperature, i.e.
- This annealing time t A is preferably of more than 60 s but does not need to be of more than 300 s.
- the quenching temperature is between 240°C and 310°C in order to have a structure containing between 10 and 40% of austenite, between 60% and 90% of martensite and between 0% and 20% of ferrite, at that temperature QT just after cooling.
- the quenching temperature QT is lower than 240°C, the fraction of the partitioned martensite in the final structure is too high to stabilize a sufficient amount of retained austenite above 9%, so that the total elongation does not reach 12%. Moreover, if the quenching temperature QT is higher than 310°C, the fraction of partitioned martensite is too low to obtain the desired tensile and yield strengths.
- the reheating rate can be high when the reheating is made by induction heater. If the partitioning temperature PT is lower than 400°C, the elongation is not satisfactory.
- This treatment allows obtaining a final structure i.e. after partitioning and cooling to the room temperature, consisting of:
- the retained austenite may comprise blocky retained austenite and film-type retained austenite, located between martensite laths.
- the blocky type retained austenite has an average aspect ratio comprised between 2 and 4.
- the film-type retained austenite has an average aspect ratio comprised between 5 and 8.
- this treatment allows obtaining an increased C content in the retained austenite, which is of at least 0.9%, preferably even of at least 1 .0%, and up to 1 .2%.
- the steel sheets thus obtained can be used as uncoated sheets or can be coated with a metallic coating such as zinc or zinc alloy, produced by electroplating or vacuum deposition.
- T A is the annealing temperature
- t A is the annealing time
- QT the quenching temperature
- PT the partitioning temperature
- Pt the maintaining time at the partitioning temperature
- YS the yield strength
- TS the tensile strength
- UE the uniform elongation
- TE the total elongation
- HER the hole expansion ratio measured according to the ISO standard.
- RA is the fraction of retained austenite in the microstructure
- C RA % is the C content in the retained austenite.
- Examples 1 to 4 show that only a quenching temperature between 240°C and 31 0°C allows obtaining a yield strength between 830 and 1 1 00 MPa, a tensile strength of at least 1 1 80 MPa, a total elongation of at least 1 2% and a hole expansion ratio of at least 30%.
- Examples 8 to 1 2 show that the targeted properties can be obtained over a wide range of partitioning times, and more specifically that the mechanical properties obtained are very stable when the partitioning time is changed.
- the tests were performed using the minimum and the maximum line speeds, with a quenching temperature QT of 250°C and a partitioning temperature PT of 450°C, or a quenching temperature QT of 300°C and a partitioning temperature PT of 400°C.
- the tests were performed with a heat-treatment comprises batch annealing at a temperature of 650°C (Heat-treatment 1 ), or with a heat-treatment comprising slow cooling of the hot-rolled steel sheet from the coiling temperature to room temperature for a time of 7 days (Heat-treatment 2).
- Tests 17 to 20 in Table III below were performed with a quenching temperature QT of 250°C and a partitioning temperature PT of 460°C, the partitioning time being either 150 s (examples 20 and 21 ) or 200 s (examples 22 and 23).
- Tests 21 to 24 in Table III were performed with a quenching temperature QT of 300°C and a partitioning temperature PT of 400°C, the partitioning time being either 150 s (examples 21 and 22) or 200 s (examples 23 and 24).
- Tests were also performed to determine the minimum cooling rate for the quenching to the quenching temperature QT.
Abstract
A method for producing a steel sheet having a microstructure consisting of between 71% and 91% of the sum of martensite and bainite, between 9% and 13% of retained austenite, and at most 20% of ferrite, the method comprising: providing a cold-rolled steel sheet, the chemical composition of the steel containing in weight %: 0.13% ≤ C ≤ 0.22%, 1.2% ≤ Si ≤ 2.3% 0.02% ≤ Al ≤ 1.0%, with 1.25% ≤ Si+Al ≤ 2.35%, 2.4% ≤ Mn ≤ 3%, Ti ≤ 0.05 % Nb ≤ 0.05 % the remainder being Fe and unavoidable impurities, annealing the steel sheet at an annealing temperature TA so as to obtain a structure comprising from 80% to 100% of austenite and from 0% to 20% of ferrite, quenching the sheet at a cooling rate comprised between 20°C/s and 50°C/s down to a quenching temperature QT between 240°C and 310°C, heating the sheet up to a partitioning temperature PT between 400°C and 465°C and maintaining the sheet at this temperature for a partitioning time Pt between 50 s and 250 s, immediately cooling the sheet down to the room temperature.
Description
METHOD FOR PRODUCING A HIGH STRENGTH STEEL SHEET HAVING IMPROVED STRENGTH AND FORMABILITY, AND OBTAINED HIGH STRENGTH STEEL SHEET
The present invention relates to a method for producing a high strength steel sheet having improved strength, ductility and formability and to the sheets obtained with the method.
To manufacture various equipments such as parts of body structural members and body panels for automotive vehicles, it is usual to use sheets made of DP (dual phase) steels or TRIP (transformation induced plasticity) steels.
For example, such steels which have include a martensitic structure and/or retained austenite and which contains about 0.2% of C, about 2% of Mn, about 1 .7% of Si have a yield strength of about 750 MPa, a tensile strength of about 980 MPa, a total elongation of more than 8%. These sheets are produced on continuous annealing line by quenching from an annealing temperature higher than Ac3 transformation point, down to an overaging above Ms transformation point and maintaining the sheet at the temperature for a given time.
To reduce the weight of the automotive in order to improve their fuel efficiency in view of the global environmental conservation it is desirable to have sheets having improved yield and tensile strength. But such sheets must also have a good ductility and a good formability and more specifically a good stretch flangeability.
In this respect, it is desirable to have sheets having a yield strength YS comprised between 830 MPa and 1 100 MPa, preferably at least 850 MPa, a tensile strength TS of at least 1 180 MPa, a total elongation of at least 12%, and preferably of at least 14%, and a hole expansion ratio HER according to ISO standard 16630:2009 of more than 30%. It must be emphasized that, due to differences in the methods of measure, the values of hole expansion ration HER according to the ISO standard are very different and not comparable to the values of the hole expansion ratio λ according to the JFS T 1001 (Japan Iron and Steel Federation standard). The tensile strength TS and the total elongation TE are measured according to ISO standard ISO 6892-1 , published in October 2009. Due to differences in the methods of measurement, in particular due to differences in the geometry of the specimen used, the values of the total elongation TE measured according to the ISO standard are very different, in particular lower, than the values of the total elongation measured according to the JIS Z 2201 -05 standard.
Therefore, the purpose of the present invention is to provide such a sheet and a method to produce it.
For this purpose, the invention relates to a method for producing a steel sheet having a microstructure consisting of between 71 % and 91 % of the sum of martensite and bainite, between 9% and 13% of retained austenite, and at most 20% of ferrite, the method comprising the following successive steps:
- providing a cold-rolled steel sheet, the chemical composition of the steel containing in weight %:
0.13%≤C≤0.22%
1 .2%≤ Si≤ 2.3%
0.02%≤AI≤ 1 .0%,
with 1 .25%≤ Si+AI≤ 2.35%,
2.4%≤ Mn≤ 3%,
Ti < 0.05 %
Nb < 0.05 %
the remainder being Fe and unavoidable impurities,
- annealing the steel sheet at an annealing temperature TA so as to obtain a structure comprising from 80% to 100% of austenite and from 0% to 20% of ferrite,
- quenching the sheet at a cooling rate comprised between 20°C/s and 50°C/s down to a quenching temperature QT between 240°C and 310°C,
- heating the sheet up to a partitioning temperature PT between 400°C and 465°C and maintaining the sheet at this temperature for a partitioning time Pt between 50 s and
250 s,
- immediately cooling the sheet down to the room temperature.
Preferably, the step of providing the cold-rolled steel sheet comprises:
- hot rolling a sheet made of said steel to obtain a hot rolled steel sheet,
- coiling said hot-rolled steel sheet at a temperature Tc comprised between
500°C and 730°C,
- cold rolling said hot-rolled steel sheet to obtain said cold-rolled steel sheet. According to a particular embodiment, the step of providing said cold-rolled steel sheet further comprises, between the coiling and the cold-rolling, performing a batch annealing at a temperature comprised between 500°C and 650°C for a time between 300 seconds and 12 hours.
According to another particular embodiment, the step of providing said cold-rolled steel sheet further comprises, between the coiling and the cold-rolling, performing a comprises slow cooling of the hot-rolled steel sheet from the coiling temperature to room temperature for a time comprised between 5 and 7 days.
Preferably, the quenched sheet has, just before the heating to the partitioning temperature PT, a structure consisting of between 10 and 40% of austenite, between 60% and 90% of martensite, and between 0% and 20% of ferrite.
According to a particular embodiment, the quenching temperature QT is comprised between 240°C and 270°C, and the partitioning temperature PT is comprised between 440°C and 460°C.
According to another particular embodiment, the quenching temperature QT is comprised between 290°C and 320°C, and the partitioning temperature PT is comprised between 400°C and 425°C.
Preferably, the chemical composition of the steel satisfies at least one of the following conditions: C > 0.16%, C < 0.20%, Si > 2.0%, Si < 2.2 %, Mn > 2.6%, Mn < 2.8%.
Preferably, after the sheet is quenched to the quenching temperature QT and before the sheet is heated to the partitioning temperature PT, the sheet is held at the quenching temperature QT for a holding time comprised between 2 s and 8 s, preferably between 3 s and 7s.
Preferably, the partitioning time Pt is between 50 and 200 s.
The invention also relates to a steel sheet, wherein the chemical composition of the steel contains in weight %:
0.13%≤C≤0.22%
1 .2%≤ Si≤ 2.3%
0.02%≤ Al≤ 1 .0%,
with 1 .25%≤ Si+AI≤ 2.35%,
2.4%≤ Mn≤ 3%,
Ti < 0.05 %
Nb < 0.05 %
the remainder being Fe and unavoidable impurities,
having a microstructure consisting of, in surface percentage:
- between 71 % and 91 % of martensite and bainite,
- between 9% and 13% of retained austenite,
- at most 20% of ferrite,
the sheet having a yield strength comprised between 850 and 1 100 MPa, a tensile strength of at least 1 180 MPa, a total elongation of at least 12% and a hole expansion ratio HER of at least 30%.
According to a particular embodiment, the total elongation TE is at least 14%, and/or the hole expansion ratio HER is greater than 40%.
The chemical composition of the steel can, optionally, satisfy at least one of the following conditions: C > 0.16 %, C < 0.20 %, Si > 2.0 %, Si < 2.2 %, Mn > 2.6 % and Mn < 2.8%.
Preferably, the C content CRA% in the retained austenite, is comprised between 0.9% and 1 .2%.
According to a particular embodiment, the retained austenite comprises blocky retained austenite having an aspect ratio comprised between 2 and 4 and film-type retained austenite having an aspect ratio comprised between 5 and 8.
Preferably, the microstructure comprises between 5.5% and 10.5% of film-type retained austenite.
According to an embodiment, the sheet is coated with a metallic coating fabricated by electroplating or vacuum deposition process.
The invention will now be described in details but without introducing limitations. The composition of the steel according to the invention comprises, in weight percent: - 0.13 to 0.22% of carbon for ensuring a satisfactory strength and improving the stability of the retained austenite which is necessary to obtain a sufficient elongation. Preferably, the carbon content is higher than or equal to 0.16%, and preferably lower than or equal to 0.20%. If the carbon content is too high, the hot rolled sheet is too hard to cold roll and the weldability is insufficient. If the carbon content is below 0.13 %, yield and tensile strength levels will not reach respectively 850 and 1 180 MPa.
- 2.4% to 3% and preferably more than 2.6% and preferably less than 2.8% of manganese. The minimum is defined to have a sufficient hardenability in order to obtain a microstructure containing at least 71 % of martensite and bainite, and a tensile strength of more than 1 180 MPa. The maximum is defined to avoid having segregation issues which are detrimental for the ductility.
- 1 .2% to 2.3% of silicon in order to stabilize the austenite, to provide a solid solution strengthening and to delay the formation of carbides during overaging without formation of silicon oxides at the surface of the sheet which would be detrimental to coatability. Preferably, the silicon content is higher than or equal to 1 .9%, still preferably higher than or equal to 2.0%. An increased amount of silicon improves the hole expansion ratio. Preferably, the silicon content is lower than or equal to 2.2%. A silicon content above 2.3% would lead to formation of silicon oxides at the surface.
- 0.02% to 1 .0% of aluminum. Aluminum is added to deoxidize the liquid steel and it increases the robustness of the manufacturing method, in particular reduces the variations of the austenite fraction when the annealing temperature varies. The maximum aluminum content is defined to prevent an increase of the Ac3 transformation point to a temperature
which would render the annealing more difficult. Aluminum, as silicon, delays the formation of carbides during carbon redistribution from martensite to austenite resulting from the overaging. To delay the formation of carbides the minimum content of Al+Si should be 1 .25%. The maximum content of Al+Si should be 2.35%.
The balance is iron and residual elements resulting from the steelmaking. In this respect, Ni, Cr, Mo, Cu, Nb, Ti, V, B, S, P and N at least are considered as residual elements which are unavoidable impurities. Therefore, their contents are less than 0.05% for Ni, 0.05% for Cr, 0.02% for Mo, 0.03% for Cu, 0.007% for V, 0.0010% for B, 0.005% for S, 0.02% for P and 0.010% for N. The Nb content is limited to 0.05% and the Ti content is limited to 0.05% because above such values, large precipitates would form and the formability of the steel would decrease, making the 12% target for the total elongation more difficult to reach.
Hot rolled sheet having a thickness between 2 and 5 mm can be produced in a known manner from this steel. As an example, the reheating temperature before rolling can be between 1200°C and 1280°C, preferably about 1250°C, the finish rolling temperature is preferably less than 850°C, the start cooling temperature less than 800°C, the stop cooling temperature between 570°C and 590°C and the coiling is performed at a temperature preferably comprised between 500°C and 730°C.
After hot rolling, the sheet is heat treated in order to reduce the strain in the steel and therefore improve the cold-rollability of the hot-rolled and coiled steel sheet.
According to a first embodiment, this heat-treatment is a batch annealing. In this embodiment, the hot-rolled and coiled steel sheet is batch annealed at a temperature between 500°C and 650°C for a time between 300 seconds and 12 hours, preferably for 4 hours to 12 hours.
According to a second embodiment, the heat-treatment is a slow cooling from the coiling temperature to the room temperature, at a cooling rate such that the sheet is cooled from the coiling temperature to the room temperature in a cooling time comprised between 5 and 7 days.
The hot rolled sheet can be pickled and cold rolled to obtain a cold rolled sheet having a thickness between 0.5 mm and 2.5 mm.
Then, the sheet is heat treated on a continuous annealing line.
The heat treatment comprises the steps of:
- annealing the sheet at an annealing temperature TA such that, at the end of the annealing step, the steel has a structure comprising at least 80% of austenite, preferably at least 95%, and up to 100%. One skilled in the art knows how to determine the annealing temperature TA from dilatometry tests. Preferably, the annealing temperature TA
is of at most Ac3 + 50°C, in order to limit the coarsening of the austenitic grains. Still preferably, the annealing temperature TA is of at most Ac3. Ac3 designates the temperature of start and the end of the transformation into austenite during the heating step. The sheet is maintained at the annealing temperature, i.e. maintained between TA - 5°C and TA + 10°C, for an annealing time tA sufficient to homogenize the chemical composition. This annealing time tA is preferably of more than 60 s but does not need to be of more than 300 s.
- quenching the sheet down to a quenching temperature QT lower than the Ms transformation point of the austenite, at a cooling rate fast enough to avoid the formation of new ferrite and bainite. The cooling rate is comprised between 20°C/s and 50°C/s. Indeed, a cooling rate lower than 20°C/s would lead to the formation of ferrite and would not allow obtaining a tensile strength of at least 1 180 MPa. The quenching temperature is between 240°C and 310°C in order to have a structure containing between 10 and 40% of austenite, between 60% and 90% of martensite and between 0% and 20% of ferrite, at that temperature QT just after cooling. If the quenching temperature QT is lower than 240°C, the fraction of the partitioned martensite in the final structure is too high to stabilize a sufficient amount of retained austenite above 9%, so that the total elongation does not reach 12%. Moreover, if the quenching temperature QT is higher than 310°C, the fraction of partitioned martensite is too low to obtain the desired tensile and yield strengths.
- optionally holding the quenched sheet at the quenching temperature for a holding time comprised between 2 s and 8 s, preferably between 3 s and 7 s.
- reheating the sheet from the quenching temperature up to a partitioning temperature PT between 400°C and 465°C. The reheating rate can be high when the reheating is made by induction heater. If the partitioning temperature PT is lower than 400°C, the elongation is not satisfactory.
- maintaining the sheet at the partitioning temperature PT for a time between 50 s and 250 s.
- immediately after this maintaining step, cooling the sheet to the room temperature, at a cooling speed preferably higher than 1 °C/s, for example between 2°C/s and 20°C/s.
This treatment allows obtaining a final structure i.e. after partitioning and cooling to the room temperature, consisting of:
- retained austenite, with a surface percentage comprised between 9 % and 13%,
martensite and bainite, with a surface percentage between 71 % and 91 %, preferably between 82 % and 91 %,
- at most 20% of ferrite, preferably at most 5%.
A fraction of retained austenite of at least 9% allows obtaining a total elongation of at least 12%, and a fraction of martensite and bainite of at least 71 % allows obtaining a tensile strength of at least 1 180 MPa.
The retained austenite may comprise blocky retained austenite and film-type retained austenite, located between martensite laths.
The blocky type retained austenite has an average aspect ratio comprised between 2 and 4. The film-type retained austenite has an average aspect ratio comprised between 5 and 8.
The aspect ratios of each of the blocky-type and film-type retained austenite is determined on the final sheet by etching with Klemm agent, then observing at least 10 micrographs with a magnification of 500 and performing image analysis of the micrographs for the identification of N constituents (i) of retained austenite. The maximal (lmax)i and minimal (Irnin), sizes of each constituent (i) are determined, and the aspect ratio of each individual constituent (i) is calculated as (lmax)i/(lmin)j, in the total population of N constituents. The average aspect ratio is calculated as the arithmetical mean value of the N individual values of (lmax)i/(lmin)i.
Preferably, the microstructure comprises between 5.5% and 10.5% of film-type retained austenite, and at most 7.5% of blocky-type austenite. Film-type retained austenite is more stable than blocky-austenite, and does not quickly transform to martensite during deformation.
Moreover, the average size of the blocks of bainite or martensite is preferably of 10 μηι or less.
Furthermore, this treatment allows obtaining an increased C content in the retained austenite, which is of at least 0.9%, preferably even of at least 1 .0%, and up to 1 .2%.
With such treatment, sheets having a yield strength YS comprised between 850 and
1 100 MPa, a tensile strength of at least 1 180 MPa, a total elongation of at least 12% and a hole expansion ratio HER according to the ISO standard 16630:2009 of at least 30% can be obtained.
According to a first preferred embodiment, the quenching temperature QT is comprised between 240°C and 270°C, and the partitioning temperature PT is comprised between 440°C and 460°C. This first embodiment allows reaching the aimed mechanical properties for a given composition over a very wide range of annealing and partitioning times, and therefore is very stable when the line speed is varied. In particular, this first embodiment provides a heavy tempering of the martensite, which results in high values of the yield strength and of the hole expansion ratio.
According to a second embodiment, the quenching temperature QT is comprised between 290°C and 320°C, and the partitioning temperature PT is comprised between 390°C and 425°C. This embodiment allows obtaining the aimed mechanical properties over a wide range of annealing and partitioning times.
The steel sheets thus obtained can be used as uncoated sheets or can be coated with a metallic coating such as zinc or zinc alloy, produced by electroplating or vacuum deposition.
Examples:
Sheets made of a steel having a composition comprising 0.163% of C, 2.05% of Si,
2.7% of Mn, and 0.02% of Al, the remainder being Fe and impurities, were produced by hot rolling, followed by coiling at 730°C. The hot rolled sheets were batch annealed at 650°C for 10 hours, then pickled and cold rolled to obtain sheets having a thickness of 1 .6 mm. The Ac1 , Ac3 and Ms points of the steel were determined by dilatometry tests, as being Ac1 =780°C, Ac3=900°C and Ms=330°C.
Several sheets were heat treated by annealing at a temperature TA for a time tA, quenching at a temperature QT at a cooling rate of 45°C/s, reheated to a partitioning temperature PT and maintained at the partitioning PT for a partitioning time Pt, then immediately cooled to room temperature.
In the tables below, TA is the annealing temperature, tA is the annealing time, QT the quenching temperature, PT the partitioning temperature, Pt the maintaining time at the partitioning temperature, YS the yield strength, TS the tensile strength, UE the uniform elongation, TE the total elongation and HER the hole expansion ratio measured according to the ISO standard. RA is the fraction of retained austenite in the microstructure, and CRA% is the C content in the retained austenite.
All examples are related to uncoated sheets.
The heat treatment conditions and the obtained properties are reported in table I. The values underlined are not according to the invention.
Table I
Examples 1 to 4 show that only a quenching temperature between 240°C and 31 0°C allows obtaining a yield strength between 830 and 1 1 00 MPa, a tensile strength of at least 1 1 80 MPa, a total elongation of at least 1 2% and a hole expansion ratio of at least 30%.
The comparison of examples 5 to 7 shows that only a partitioning temperature PT comprised between 400°C and 465°C allows obtaining the targeted properties, whereas a partitioning temperature PT above 465°C leads to the formation of a high fraction of fresh martensite, which leads to a hole expansion ratio below 30%.
These examples 1 to 7 further show that when the quenching temperature QT is comprised between 290°C and 320°C and the partitioning temperature PT is comprised between 400°C and 425°C, a total elongation of more than 14% can be reached.
Examples 8 to 1 2 show that the targeted properties can be obtained over a wide range of partitioning times, and more specifically that the mechanical properties obtained are very stable when the partitioning time is changed.
These examples further show that when the quenching temperature QT is comprised between 240°C and 270°C, and the partitioning temperature PT is comprised
between 440°C and 460°C, very high values of yield strength are obtained. These high values are due to an important tempering of the martensite, owing to the low value of the quenching temperature QT and to the high value of the partitioning temperature PT.
Further tests were performed to study the influence of the line speed on the mechanical properties of the sheet during the manufacture, i.e. the stability of these mechanical properties with variations of the line speed.
These tests were performed on a line having a minimum line speed of 50 m/min and a maximum line speed of 120 m/min, with soaking and partitioning sections configured so that the maximum soaking time and partitioning time, reached with the minimum line speed, are respectively of 188 s and 433 s. the minimum soaking time and partitioning time, reached with the maximum line speed, are respectively 79 s and 181 s.
The tests were performed using the minimum and the maximum line speeds, with a quenching temperature QT of 250°C and a partitioning temperature PT of 450°C, or a quenching temperature QT of 300°C and a partitioning temperature PT of 400°C.
The heat treatment conditions and the obtained properties are reported in table II.
Table II
These results show that with a quenching temperature QT of 250°C and a partitioning temperature PT of 450°C, the line speed has little influence on the quality of the mechanical properties obtained, so that the targeted properties can be obtained throughout the whole range of line speeds. These results also show that the manufacturing process is very robust with regard to variations of the line speed.
The results obtained with a quenching temperature QT of 300°C and a partitioning temperature PT of 400°C are similar, even if the yield strength is slightly lower than the targeted value of 850 MPa when the line speed is too slow and the partitioning temperature consequently longer than 250 s.
These results further show that when the quenching temperature QT is comprised between 290°C and 320°C and the partitioning temperature PT is comprised between
400°C and 425°C, or when the quenching temperature QT is comprised between 240°C and 270°C, and the partitioning temperature PT is comprised between 440°C and 460°C, a total elongation of more than 14% can be reached.
Tests were further performed to assess the effect of the heat-treatment performed between the coiling and the cold-rolling steps.
The tests were performed with a heat-treatment comprises batch annealing at a temperature of 650°C (Heat-treatment 1 ), or with a heat-treatment comprising slow cooling of the hot-rolled steel sheet from the coiling temperature to room temperature for a time of 7 days (Heat-treatment 2).
Tests 17 to 20 in Table III below were performed with a quenching temperature QT of 250°C and a partitioning temperature PT of 460°C, the partitioning time being either 150 s (examples 20 and 21 ) or 200 s (examples 22 and 23).
Tests 21 to 24 in Table III were performed with a quenching temperature QT of 300°C and a partitioning temperature PT of 400°C, the partitioning time being either 150 s (examples 21 and 22) or 200 s (examples 23 and 24).
These tests show that the targeted mechanical properties are obtained by a process according to the invention if the heat-treatment performed between the coiling and the cold-rolling steps is a batch annealing or a slow cooling.
These tests further confirm that a quenching temperature QT comprised between 240°C and 270°C and a partitioning temperature PT comprised between 440°C and 460°, or a quenching temperature QT comprised between 290°C and 320°C, and a partitioning temperature PT comprised between 400°C and 425°C, allow obtaining very satisfactory mechanical properties, in particular a total elongation of more than 14%.
Tests were also performed to determine the minimum cooling rate for the quenching to the quenching temperature QT.
The heat treatment conditions and the obtained properties are reported in table IV.
In this table, CR designates the cooling rate.
Table IV
These results show that when the cooling rate is below 20°C/s, a tensile strength of less than 1 180 MPa is obtained, whereas the mechanical properties are satisfactory when the cooling rate is comprised between 20°C/s and 50°C/s.
Claims
1 . - A method for producing a steel sheet having a microstructure consisting of between 71 % and 91 % of the sum of martensite and bainite, between 9% and 13% of retained austenite, and at most 20% of ferrite, wherein the method comprises the following successive steps:
- providing a cold-rolled steel sheet, the chemical composition of the steel containing in weight %:
0.13%≤C≤0.22%
1 .2%≤ Si≤ 2.3%
0.02%≤AI≤ 1 .0%,
with 1 .25%≤ Si+AI≤ 2.35%,
2.4%≤ Mn≤ 3%,
Ti < 0.05 %
Nb < 0.05 %
the remainder being Fe and unavoidable impurities,
- annealing the steel sheet at an annealing temperature TA so as to obtain a structure comprising from 80% to 100% of austenite and from 0% to 20% of ferrite,
- quenching the sheet at a cooling rate comprised between 20°C/s and 50°C/s down to a quenching temperature QT between 240°C and 310°C,
- heating the sheet up to a partitioning temperature PT between 400°C and 465°C and maintaining the sheet at the partitioning temperature PT for a partitioning time Pt between 50 s and 250 s,
- immediately cooling the sheet down to the room temperature.
2. - The method according to claim 1 , wherein the step of providing said cold-rolled steel sheet comprises:
- hot rolling a sheet made of said steel to obtain a hot rolled steel sheet,
- coiling said hot-rolled steel sheet at a temperature Tc comprised between 500°C and 730°C,
- cold rolling said hot-rolled steel sheet to obtain said cold-rolled steel sheet.
3. - The method according to claim 2, wherein the step of providing said cold-rolled steel sheet further comprises, between the coiling and the cold-rolling, performing a batch annealing at a temperature comprised between 500°C and 650°C for a time between 300 seconds and 12 hours.
4. - The method according to claim 2, wherein the step of providing said cold-rolled steel sheet further comprises, between the coiling and the cold-rolling, performing a comprises slow cooling of the hot-rolled steel sheet from the coiling temperature to room temperature for a time comprised between 5 and 7 days.
5. - The method according to any one of claims 1 to 4, wherein the quenched sheet has, just before the heating to the partitioning temperature PT, a structure consisting of between 10 and 40% of austenite, between 60% and 90% of martensite and between 0% and 20% of ferrite.
6. - The method according to any one of claims 1 to 5, wherein the quenching temperature QT is comprised between 240°C and 270°C, and the partitioning temperature PT is comprised between 440°C and 460°C.
7. - The method according to any one of claims 1 to 5, wherein the quenching temperature QT is comprised between 290°C and 320°C, and the partitioning temperature PT is comprised between 400°C and 425°C. 8 - The method according to any one of claims 1 to 7, wherein the chemical composition of the steel satisfies at least one of the following conditions:
C > 0.16 %,
C < 0.20 %,
Si > 2.0 %,
Si < 2.2 %,
Mn > 2.6 %,
and
Mn < 2.
8%.
9.- The method according to any one of claims 1 to 8, wherein, after the sheet is quenched to the quenching temperature QT and before the sheet is heated to the partitioning temperature PT, the sheet is held at the quenching temperature QT for a holding time comprised between 2 s and 8 s, preferably between 3 s and 7s.
10.- The method according to any one of claims 1 to 9, wherein the partitioning time
Pt is between 50 and 200 s.
1 1 .- A steel sheet wherein the chemical composition of the steel contains in weight
%
0.13%≤C≤ 0.22%
1 .2%≤ Si≤ 2.3%
0.02%≤ Al≤ 1 .0%,
with 1 .25%≤ Si+AI≤ 2.35%,
2.4%≤ Mn≤ 3%,
Ti < 0.05 %
Nb < 0.05 %
the remainder being Fe and unavoidable impurities,
having a microstructure consisting of, in surface percentage:
- between 71 % and 91 % of martensite and bainite,
- between 9% and 13% of retained austenite,
- at most 20% of ferrite,
the sheet having a yield strength comprised between 850 and 1 100 MPa, a tensile strength of at least 1 180 MPa, a total elongation of at least 12% and a hole expansion ratio HER of at least 30%.
12.- The steel according to claim 1 1 , wherein the total elongation TE is at least 14%.
13. - The steel sheet according to any one of claims 1 1 or 12, wherein the hole expansion ratio HER is greater than 40%.
14. - The steel sheet according to any one of claims 1 1 to 13, wherein the chemical composition of the steel satisfies at least one of the following conditions:
C > 0.16 %,
C < 0.20 %,
Si > 2.0 %,
Si < 2.2 %,
Mn > 2.6 %,
and
Mn < 2.8%.
15.- The steel sheet according to any one of claims 1 1 to 14, wherein the C CRA% in the retained austenite, is comprised between 0.9% and 1 .2%.
16.- The steel sheet according to any one of claims 1 1 to 15, wherein the retained austenite comprises blocky retained austenite having an aspect ratio comprised between 2 and 4 and film-type retained austenite having an aspect ratio comprised between 5 and 8.
17.- The steel sheet according to claim 16, wherein the microstructure comprises between 5.5% and 10.5% of film-type retained austenite.
18- The steel sheet according to any one of claims 1 1 to 17, wherein the sheet is coated with a metallic coating fabricated by electroplating or vacuum deposition process.
Priority Applications (21)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/IB2015/059838 WO2017109539A1 (en) | 2015-12-21 | 2015-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
MA44113A MA44113B1 (en) | 2015-12-21 | 2016-12-21 | A method of producing a high strength steel sheet having improved strength and formability and high strength steel sheet thereby obtained |
EP16820260.4A EP3394299B1 (en) | 2015-12-21 | 2016-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
CN201680074868.3A CN108884512B (en) | 2015-12-21 | 2016-12-21 | Method for producing high-strength steel sheet with improved strength and formability and high-strength steel sheet obtained |
KR1020187017055A KR20180095529A (en) | 2015-12-21 | 2016-12-21 | A method for producing a high strength steel sheet having improved strength and moldability, and a method for producing the high strength steel sheet |
ES16820260T ES2801673T3 (en) | 2015-12-21 | 2016-12-21 | Process to produce high-strength steel sheet with improved strength and formability, and the obtained high-strength steel sheet |
MA49159A MA49159B1 (en) | 2015-12-21 | 2016-12-21 | A method of producing a high strength steel sheet having improved strength and formability and a high strength steel sheet thereby obtained |
HUE19207907A HUE056872T2 (en) | 2015-12-21 | 2016-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
PCT/EP2016/082202 WO2017108966A1 (en) | 2015-12-21 | 2016-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
HUE16820260A HUE050422T2 (en) | 2015-12-21 | 2016-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
PL19207907T PL3626843T3 (en) | 2015-12-21 | 2016-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
EP19207907.7A EP3626843B1 (en) | 2015-12-21 | 2016-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
BR112018011653-0A BR112018011653B1 (en) | 2015-12-21 | 2016-12-21 | METHODS FOR PRODUCING A STEEL SHEET, UNCOATED STEEL SHEET AND STEEL SHEET |
RU2018122307A RU2722490C2 (en) | 2015-12-21 | 2016-12-21 | Method of producing high-strength sheet steel, characterized by improved strength and moldability, and obtained high-strength sheet steel |
CA3007647A CA3007647C (en) | 2015-12-21 | 2016-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
US16/064,545 US10954580B2 (en) | 2015-12-21 | 2016-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
PL16820260T PL3394299T3 (en) | 2015-12-21 | 2016-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
MX2018007641A MX2018007641A (en) | 2015-12-21 | 2016-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet. |
JP2018551522A JP6797934B2 (en) | 2015-12-21 | 2016-12-21 | A method for manufacturing a high-strength steel sheet with improved strength and formability, and the obtained high-strength steel sheet. |
ES19207907T ES2886206T3 (en) | 2015-12-21 | 2016-12-21 | Production process of high-strength steel sheet with improved strength and formability, and the obtained high-strength steel sheet |
ZA2018/03701A ZA201803701B (en) | 2015-12-21 | 2018-06-04 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/IB2015/059838 WO2017109539A1 (en) | 2015-12-21 | 2015-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2017109539A1 true WO2017109539A1 (en) | 2017-06-29 |
Family
ID=55221457
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB2015/059838 WO2017109539A1 (en) | 2015-12-21 | 2015-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
PCT/EP2016/082202 WO2017108966A1 (en) | 2015-12-21 | 2016-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/EP2016/082202 WO2017108966A1 (en) | 2015-12-21 | 2016-12-21 | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet |
Country Status (15)
Country | Link |
---|---|
US (1) | US10954580B2 (en) |
EP (2) | EP3394299B1 (en) |
JP (1) | JP6797934B2 (en) |
KR (1) | KR20180095529A (en) |
CN (1) | CN108884512B (en) |
BR (1) | BR112018011653B1 (en) |
CA (1) | CA3007647C (en) |
ES (2) | ES2886206T3 (en) |
HU (2) | HUE050422T2 (en) |
MA (2) | MA44113B1 (en) |
MX (1) | MX2018007641A (en) |
PL (2) | PL3626843T3 (en) |
RU (1) | RU2722490C2 (en) |
WO (2) | WO2017109539A1 (en) |
ZA (1) | ZA201803701B (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN111373061A (en) * | 2017-12-05 | 2020-07-03 | 安赛乐米塔尔公司 | Cold-rolled annealed steel sheet and method for producing same |
CN111433376A (en) * | 2017-12-05 | 2020-07-17 | 安赛乐米塔尔公司 | Cold-rolled annealed steel sheet and method for producing same |
CN113446942A (en) * | 2021-08-11 | 2021-09-28 | 镇江龙源铝业有限公司 | Method for rapidly detecting blow-up forming performance of cold-rolled aluminum alloy plate strip |
Families Citing this family (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2016001708A1 (en) | 2014-07-03 | 2016-01-07 | Arcelormittal | Method for producing a high strength coated steel sheet having improved strength, formability and obtained sheet |
DE102016103752A1 (en) * | 2015-03-06 | 2016-09-08 | Gkn Sinter Metals, Llc | Process for producing a brass or bronze composite component by means of sintered fit |
KR102012126B1 (en) * | 2018-03-22 | 2019-10-21 | 현대제철 주식회사 | Ultra high strength cold rolled steel sheet and method for manufacturing the same |
MX2021004073A (en) | 2018-10-10 | 2021-06-04 | Jfe Steel Corp | High-strength steel sheet and method for manufacturing same. |
RU2768717C1 (en) * | 2018-11-30 | 2022-03-24 | Арселормиттал | Cold-rolled annealed steel sheet with high degree of hole expansion and method of its manufacturing |
EP3754037B1 (en) * | 2019-06-17 | 2022-03-02 | Tata Steel IJmuiden B.V. | Method of heat treating a high strength cold rolled steel strip |
JP7191796B2 (en) * | 2019-09-17 | 2022-12-19 | 株式会社神戸製鋼所 | High-strength steel plate and its manufacturing method |
KR102285523B1 (en) * | 2019-11-20 | 2021-08-03 | 현대제철 주식회사 | Steel sheet having high strength and high formability and method for manufacturing the same |
EP4116003A4 (en) * | 2020-03-11 | 2023-06-21 | Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) | Method for manufacturing steel component having locally softened section |
KR20230145590A (en) * | 2021-03-08 | 2023-10-17 | 가부시키가이샤 고베 세이코쇼 | Manufacturing method of steel plate |
CN113061698B (en) * | 2021-03-16 | 2022-04-19 | 北京理工大学 | Heat treatment method for preparing quenching-partitioning steel by taking pearlite as precursor |
KR20230166357A (en) | 2022-05-30 | 2023-12-07 | 현대제철 주식회사 | A method of manufacturing steel sheet with high corrosion resistance steel sheet and Manufacturing Method Thereof |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2325346A1 (en) * | 2008-09-10 | 2011-05-25 | JFE Steel Corporation | High-strength steel plate and manufacturing method thereof |
EP2757171A1 (en) * | 2011-10-07 | 2014-07-23 | JFE Steel Corporation | High-strength hot-dipped galvanized steel sheet having excellent formability and impact resistance, and method for producing same |
EP2881481A1 (en) * | 2012-07-31 | 2015-06-10 | JFE Steel Corporation | High-strength hot-dip galvanized steel sheet having excellent moldability and shape fixability, and method for manufacturing same |
JP2015224359A (en) * | 2014-05-27 | 2015-12-14 | Jfeスチール株式会社 | Method of producing high strength steel sheet |
WO2016001708A1 (en) * | 2014-07-03 | 2016-01-07 | Arcelormittal | Method for producing a high strength coated steel sheet having improved strength, formability and obtained sheet |
Family Cites Families (38)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE19936151A1 (en) | 1999-07-31 | 2001-02-08 | Thyssenkrupp Stahl Ag | High-strength steel strip or sheet and process for its manufacture |
JP3840864B2 (en) | 1999-11-02 | 2006-11-01 | Jfeスチール株式会社 | High-tensile hot-dip galvanized steel sheet and manufacturing method thereof |
JP3873642B2 (en) | 2001-03-21 | 2007-01-24 | Jfeスチール株式会社 | Tinned steel sheet |
AU2003270334A1 (en) | 2002-09-04 | 2004-03-29 | Colorado School Of Mines | Method for producing steel with retained austenite |
FR2844281B1 (en) | 2002-09-06 | 2005-04-29 | Usinor | HIGH MECHANICAL STRENGTH STEEL AND METHOD OF MANUFACTURING SHEET OF ZINC-COATED STEEL OR ZINC ALLOY STEEL |
JP4367300B2 (en) | 2004-09-14 | 2009-11-18 | Jfeスチール株式会社 | High-strength cold-rolled steel sheet excellent in ductility and chemical conversion property and method for producing the same |
CA2531615A1 (en) | 2004-12-28 | 2006-06-28 | Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) | High strength thin steel sheet having high hydrogen embrittlement resisting property |
CN100510141C (en) | 2004-12-28 | 2009-07-08 | 株式会社神户制钢所 | Ultrahigh-strength steel sheet superior in hydrogen-embrittlement resistance |
JP4821365B2 (en) | 2006-02-28 | 2011-11-24 | Jfeスチール株式会社 | Manufacturing method of high-tensile cold-rolled steel sheet with excellent corrosion resistance after painting |
UA99289C2 (en) * | 2007-05-11 | 2012-08-10 | Арселормиттал Франс | Cold-rolled and annealed steel sheet, method for its production (variants) and use |
EP1990431A1 (en) | 2007-05-11 | 2008-11-12 | ArcelorMittal France | Method of manufacturing annealed, very high-resistance, cold-laminated steel sheets, and sheets produced thereby |
JP5402007B2 (en) | 2008-02-08 | 2014-01-29 | Jfeスチール株式会社 | High-strength hot-dip galvanized steel sheet excellent in workability and manufacturing method thereof |
JP5365112B2 (en) | 2008-09-10 | 2013-12-11 | Jfeスチール株式会社 | High strength steel plate and manufacturing method thereof |
JP5221270B2 (en) | 2008-10-09 | 2013-06-26 | 株式会社東芝 | Metal parts and manufacturing method thereof |
JP5315956B2 (en) | 2008-11-28 | 2013-10-16 | Jfeスチール株式会社 | High-strength hot-dip galvanized steel sheet with excellent formability and method for producing the same |
BRPI1010678A2 (en) | 2009-05-27 | 2016-03-15 | Nippon Steel Corp | high strength steel plate, hot-plated steel plate and hot-alloy alloy steel plate which have excellent fatigue, elongation and collision characteristics, and manufacturing method for said steel plates |
JP5412182B2 (en) * | 2009-05-29 | 2014-02-12 | 株式会社神戸製鋼所 | High strength steel plate with excellent hydrogen embrittlement resistance |
JP5883211B2 (en) | 2010-01-29 | 2016-03-09 | 株式会社神戸製鋼所 | High-strength cold-rolled steel sheet with excellent workability and method for producing the same |
JP5807368B2 (en) | 2010-06-16 | 2015-11-10 | 新日鐵住金株式会社 | High-strength cold-rolled steel sheet having a very high uniform elongation in the direction of 45 ° with respect to the rolling direction and a method for producing the same |
JP5021108B2 (en) | 2010-09-16 | 2012-09-05 | 新日本製鐵株式会社 | High-strength steel sheet, high-strength galvanized steel sheet excellent in ductility and stretch flangeability, and methods for producing them |
JP5821260B2 (en) * | 2011-04-26 | 2015-11-24 | Jfeスチール株式会社 | High-strength hot-dip galvanized steel sheet excellent in formability and shape freezing property, and method for producing the same |
EP2524970A1 (en) | 2011-05-18 | 2012-11-21 | ThyssenKrupp Steel Europe AG | Extremely stable steel flat product and method for its production |
JP2012240095A (en) | 2011-05-20 | 2012-12-10 | Kobe Steel Ltd | Warm forming method of high-strength steel sheet |
US9745639B2 (en) | 2011-06-13 | 2017-08-29 | Kobe Steel, Ltd. | High-strength steel sheet excellent in workability and cold brittleness resistance, and manufacturing method thereof |
JP5664482B2 (en) | 2011-07-06 | 2015-02-04 | 新日鐵住金株式会社 | Hot-dip cold-rolled steel sheet |
JP5764549B2 (en) | 2012-03-29 | 2015-08-19 | 株式会社神戸製鋼所 | High-strength cold-rolled steel sheet, high-strength hot-dip galvanized steel sheet, high-strength galvannealed steel sheet excellent in formability and shape freezing property, and methods for producing them |
JP5632904B2 (en) * | 2012-03-29 | 2014-11-26 | 株式会社神戸製鋼所 | Manufacturing method of high-strength cold-rolled steel sheet with excellent workability |
JP5835129B2 (en) | 2012-06-29 | 2015-12-24 | トヨタ自動車株式会社 | Surface treatment method |
JP2014019928A (en) | 2012-07-20 | 2014-02-03 | Jfe Steel Corp | High strength cold rolled steel sheet and method for producing high strength cold rolled steel sheet |
EP2690183B1 (en) * | 2012-07-27 | 2017-06-28 | ThyssenKrupp Steel Europe AG | Hot-rolled steel flat product and method for its production |
EP2690184B1 (en) * | 2012-07-27 | 2020-09-02 | ThyssenKrupp Steel Europe AG | Produit plat en acier laminé à froid et son procédé de fabrication |
RU2524743C2 (en) | 2012-11-06 | 2014-08-10 | Закрытое акционерное общество "Вибро-прибор" | Method for calibration of piezoelectric vibration transducer on operation site without dismantlement |
CN102943169B (en) * | 2012-12-10 | 2015-01-07 | 北京科技大学 | Quenching and annealing preparation method of ultrahigh-strength thin steel plate for automobiles |
EP2840159B8 (en) * | 2013-08-22 | 2017-07-19 | ThyssenKrupp Steel Europe AG | Method for producing a steel component |
JP6237364B2 (en) * | 2014-03-17 | 2017-11-29 | 新日鐵住金株式会社 | High strength steel plate with excellent impact characteristics and method for producing the same |
CN104032109B (en) * | 2014-06-13 | 2016-08-24 | 北京科技大学 | A kind of high-strength steel passes through hot rolling and the preparation method of burning optimization on line |
WO2016108443A1 (en) * | 2014-12-30 | 2016-07-07 | 한국기계연구원 | High-strength steel plate having excellent combination of strength and ductility, and manufacturing method therefor |
KR102035525B1 (en) * | 2016-06-27 | 2019-10-24 | 한국기계연구원 | Steel having film type retained austenite |
-
2015
- 2015-12-21 WO PCT/IB2015/059838 patent/WO2017109539A1/en active Application Filing
-
2016
- 2016-12-21 HU HUE16820260A patent/HUE050422T2/en unknown
- 2016-12-21 ES ES19207907T patent/ES2886206T3/en active Active
- 2016-12-21 MA MA44113A patent/MA44113B1/en unknown
- 2016-12-21 PL PL19207907T patent/PL3626843T3/en unknown
- 2016-12-21 MA MA49159A patent/MA49159B1/en unknown
- 2016-12-21 CA CA3007647A patent/CA3007647C/en active Active
- 2016-12-21 PL PL16820260T patent/PL3394299T3/en unknown
- 2016-12-21 EP EP16820260.4A patent/EP3394299B1/en active Active
- 2016-12-21 KR KR1020187017055A patent/KR20180095529A/en not_active IP Right Cessation
- 2016-12-21 US US16/064,545 patent/US10954580B2/en active Active
- 2016-12-21 MX MX2018007641A patent/MX2018007641A/en unknown
- 2016-12-21 JP JP2018551522A patent/JP6797934B2/en active Active
- 2016-12-21 CN CN201680074868.3A patent/CN108884512B/en active Active
- 2016-12-21 WO PCT/EP2016/082202 patent/WO2017108966A1/en active Application Filing
- 2016-12-21 EP EP19207907.7A patent/EP3626843B1/en active Active
- 2016-12-21 HU HUE19207907A patent/HUE056872T2/en unknown
- 2016-12-21 ES ES16820260T patent/ES2801673T3/en active Active
- 2016-12-21 BR BR112018011653-0A patent/BR112018011653B1/en active IP Right Grant
- 2016-12-21 RU RU2018122307A patent/RU2722490C2/en active
-
2018
- 2018-06-04 ZA ZA2018/03701A patent/ZA201803701B/en unknown
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2325346A1 (en) * | 2008-09-10 | 2011-05-25 | JFE Steel Corporation | High-strength steel plate and manufacturing method thereof |
EP2757171A1 (en) * | 2011-10-07 | 2014-07-23 | JFE Steel Corporation | High-strength hot-dipped galvanized steel sheet having excellent formability and impact resistance, and method for producing same |
EP2881481A1 (en) * | 2012-07-31 | 2015-06-10 | JFE Steel Corporation | High-strength hot-dip galvanized steel sheet having excellent moldability and shape fixability, and method for manufacturing same |
JP2015224359A (en) * | 2014-05-27 | 2015-12-14 | Jfeスチール株式会社 | Method of producing high strength steel sheet |
WO2016001708A1 (en) * | 2014-07-03 | 2016-01-07 | Arcelormittal | Method for producing a high strength coated steel sheet having improved strength, formability and obtained sheet |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN111373061A (en) * | 2017-12-05 | 2020-07-03 | 安赛乐米塔尔公司 | Cold-rolled annealed steel sheet and method for producing same |
CN111433376A (en) * | 2017-12-05 | 2020-07-17 | 安赛乐米塔尔公司 | Cold-rolled annealed steel sheet and method for producing same |
CN111373061B (en) * | 2017-12-05 | 2022-03-11 | 安赛乐米塔尔公司 | Cold-rolled annealed steel sheet and method for producing same |
US11530459B2 (en) | 2017-12-05 | 2022-12-20 | Arcelormittal | Cold rolled and annealed steel sheet and method of manufacturing the same |
CN113446942A (en) * | 2021-08-11 | 2021-09-28 | 镇江龙源铝业有限公司 | Method for rapidly detecting blow-up forming performance of cold-rolled aluminum alloy plate strip |
CN113446942B (en) * | 2021-08-11 | 2022-03-29 | 镇江龙源铝业有限公司 | Method for rapidly detecting blow-up forming performance of cold-rolled aluminum alloy plate strip |
Also Published As
Publication number | Publication date |
---|---|
US20190003007A1 (en) | 2019-01-03 |
HUE056872T2 (en) | 2022-03-28 |
RU2018122307A3 (en) | 2020-03-26 |
HUE050422T2 (en) | 2020-12-28 |
BR112018011653A2 (en) | 2018-12-04 |
ES2886206T3 (en) | 2021-12-16 |
CA3007647C (en) | 2023-12-19 |
EP3394299B1 (en) | 2020-05-06 |
PL3626843T3 (en) | 2021-12-20 |
MA49159A (en) | 2021-04-21 |
PL3394299T3 (en) | 2020-11-02 |
US10954580B2 (en) | 2021-03-23 |
MA49159B1 (en) | 2021-10-29 |
ES2801673T3 (en) | 2021-01-12 |
KR20180095529A (en) | 2018-08-27 |
WO2017108966A1 (en) | 2017-06-29 |
EP3626843A1 (en) | 2020-03-25 |
JP6797934B2 (en) | 2020-12-09 |
ZA201803701B (en) | 2019-06-26 |
CN108884512B (en) | 2019-12-31 |
MX2018007641A (en) | 2018-09-21 |
MA44113B1 (en) | 2020-08-31 |
CN108884512A (en) | 2018-11-23 |
CA3007647A1 (en) | 2017-06-29 |
JP2019505694A (en) | 2019-02-28 |
EP3626843B1 (en) | 2021-07-28 |
BR112018011653B1 (en) | 2021-09-28 |
RU2722490C2 (en) | 2020-06-01 |
EP3394299A1 (en) | 2018-10-31 |
RU2018122307A (en) | 2019-12-30 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
CA3007647C (en) | Method for producing a high strength steel sheet having improved strength and formability, and obtained high strength steel sheet | |
JP7166396B2 (en) | Method for producing high-strength steel sheet with improved strength, ductility and formability | |
US11492676B2 (en) | Method for producing a high strength coated steel sheet having improved strength, ductility and formability | |
WO2017108959A1 (en) | Method for producing a high strength coated steel sheet having improved ductility and formability, and obtained coated steel sheet | |
KR102455376B1 (en) | Method for producing a high strength coated steel sheet having improved strength and ductility and obtained sheet | |
EP3394300A1 (en) | Method for producing a high strength steel sheet having improved ductility and formability, and obtained steel sheet | |
WO2017108897A1 (en) | Method for producing a high strength steel sheet having improved ductility and formability, and obtained steel sheet | |
KR102423654B1 (en) | Method for manufacturing a high strength steel sheet having improved formability and sheet obtained | |
EP3164514B1 (en) | Method for manufacturing a high strength steel sheet having improved formability and ductility and sheet obtained | |
EP3394296B1 (en) | Method for producing a steel sheet having improved strength, ductility and formability | |
US10907232B2 (en) | Method for producing a high strength coated steel sheet having improved strength, formability and obtained sheet |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 15828378 Country of ref document: EP Kind code of ref document: A1 |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
122 | Ep: pct application non-entry in european phase |
Ref document number: 15828378 Country of ref document: EP Kind code of ref document: A1 |